A continuing need exists to develop wideband electrooptic modulators which are capable of meeting the extended bandwidth requirements of advanced laser communication and data processing systems at reasonably modest levels of driver power. This need is particularly acute at longer infrared wavelengths such as 10.6 micrometers where conventional, diffraction limited modulator devices impose typically kilowatt levels for high modulation depths at bandwidths of 300 MHz and higher.
Prior art traveling wave electro-optic modulators of the general TEM parallel strip transmission line type have been designed for diffraction limited operation wherein the optical beam is focused through the device -- or is transmitted unfocused as a narrow collimated beam -- with a resulting limit of length to cross-section ratio substantially less than that disclosed herein. Moreover, velocity synchronism has in the past been achieved only at the expense of a low characteristic impedance as described, for example, by C. J. Peters in the "Proceedings IEEE" 51, 147 (1963).
It is an object of the present invention to alleviate the excessive driver power burden of conventional wideband electro-optic modulators used with infrared lasers such as CO.sub.2 lasers operating at 10.6 micrometers.